1. Field of the Invention
The present invention relates to an inhaler for ejecting a medicine to cause the medicine to be inhaled by a user. The present invention also relates to an ejection head unit that can be attached to the inhaler.
2. Description of the Related Art
In recent years, average life expectancy is increasing as a result of advances in the fields of medicine and science. This is leading to an increase in the elderly population. In particular, in so-called developed countries, an increase in patients with lifestyle-related diseases such as diabetes or hypertension has become a problem. On the other hand, the number of medical institutions is not increasing to a degree that can cope with the increase in these kinds of patients, and since there are some communities in which there are no medical institutions that such patients can attend, there is a concern about ways to cope with this problem in the future, including from the viewpoint of government policy.
A specific case will now be described. Among the diabetes patients that are increasing at present, patients suffering from insulin-dependent type diabetes, referred to as “type 1”, need to be regularly administered doses of insulin, since they have no secretion of insulin from their pancreas. Because administration of insulin is currently performed by subcutaneous injection, the physical and mental burden on the patient is large.
A pen-type syringe with a thin needle that causes less pain to patients has been developed to lessen the burden on this kind of user. However, in most cases patients with type 1 diabetes lead a life that is similar to a person in normal health other than requiring regular administration of insulin. Therefore, since there is generally a mental resistance to administering an injection to oneself in front of other people, even with a pen-type syringe, it may be difficult for them to perform administration at an appropriate time. Consequently, there is a concern that appropriate treatment of the user will not be achieved out with this kind of method. Meanwhile, inhalers have been developed that allow a user to inhale minute droplets of a medicine solution by utilizing the ejection principles of an ink-jet system to eject the droplets into an air flow path in which air flows that is inhaled through a mouthpiece (see International Publication No. WO1995/01137 and International Publication No. WO2002/04043). This kind of inhaler has the advantage of enabling a predetermined amount of a medicine solution to be precisely sprayed in a uniform particle size.
The basic configuration of this kind of medicine-solution ejecting apparatus includes an ejection head in which an ejection energy generating element such as a heater element is disposed and a reservoir that stores a medicine solution that is supplied to the ejection head. For both a case in which the ejection head and the reservoir are integrated to include a cartridge and a case in which the ejection head and the reservoir are provided as separate members which are independently exchangeable, it is assumed that the same ejection head will be used for inhalation a plurality of times.
However, with an inhaler it is important that the particle size of a droplet is several microns, which is an extremely small size. Thus, it is necessary that the diameter of the ejection nozzle is also several microns. When performing inhalation a plurality of times with the same ejection head, residual medicine is liable to adhere to an inner wall of the ejection nozzle and block up the ejection nozzle. Consequently, there is the problem that the number of ejection orifices that eject droplets at the time of the next inhalation is reduced and the ejection amount is less than the predetermined ejection amount. Further, the interval inhalation may involve inhalation after each meal or inhalation once per day, and in that case a problem regarding a change in the properties of the medicine or regarding hygiene arises.
To solve such problems, although it is adequate to perform a suction and restoration operation utilizing a medicine solution in a similar manner to that employed in a known ink jet printer, it is not desirable to waste a high cost medicine solution, and the size of the apparatus also increases. As a result of these problems, it is necessary to perform the troublesome work of replacing the ejection head for each inhalation, and the actual situation is that the apparatus is impractical.